The present invention relates to a method for coupling a first system component and a second system component of a measuring device, in particular a coordinate measuring device, for determining by means of a sensor a property, in particular three-dimensional coordinates and/or other specific local properties, for example roughness, color or scattering behavior, of an object to be measured, wherein an interface arrangement is provided between the first system component and the second system component, wherein the interface arrangement is provided with at least one electrical interface, formed from at least two electrical transmission paths, for transmitting a first electrical voltage between the first system component and the second system component, and with at least one optical interface formed from light waveguides.
According to another aspect, the present invention relates to a measuring device, in particular a coordinate measuring device, for determining by means of a sensor a property, in particular three-dimensional coordinates and/or other specific local properties, for example roughness, color or scattering behavior, of an object to be measured, having a first system component and a second system component, wherein an interface arrangement is formed between the first system component and the second system component, wherein the interface arrangement comprises at least one electrical interface, formed from at least two electrical transmission paths, for transmitting electrical energy between the first system component and the second system component, and at least one optical interface formed from light waveguides.
Methods for coupling system components of measuring devices and coordinate measuring devices are known, for example, from document EP 2 194 357 A1.
Coordinate measuring devices are widely known in the prior art. They are used, for example, in order to inspect workpieces in the scope of quality assurance, or in order to determine the geometry of a workpiece fully in the scope of so-called reverse engineering. Furthermore, many other possible applications may be envisioned.
In such coordinate measuring devices, various types of sensors may be used in order to acquire the coordinates of a workpiece to be measured. To this end, for example, tactilely measuring sensors are known, as are marketed for example by the Applicant under the product reference “VAST”, “VAST XT” or “VAST XTT”. In this case, the surface of the workpiece to be measured is sampled by means of a probe pin, the coordinates of which in the measurement space are constantly known. Such a probe pin may also be moved along the surface of a workpiece, so that, in such a measuring process, a multiplicity of measurement points can be acquired at fixed time intervals in the scope of a so-called scanning method.
Furthermore, it is known to use optical sensors which permit contactless acquisition of the coordinates of a workpiece. An example of such an optical sensor is the optical sensor marketed by the Applicant under the product reference “ViScan”.
The sensors may then be used in various types of measurement structures. One example of such a measurement structure is the product “O-INSPECT” of the Applicant. In such a device, both an optical sensor and a tactile sensor are used in order to carry out various inspection tasks on a machine and, ideally, with single clamping of a workpiece to be measured. In this way, all inspection tasks, for example in medical technology, plastics technology, electronics and precision mechanics, can be carried out in a straightforward way. Of course, various other structures may furthermore be envisioned as well.
Such sensor systems or sensor heads, which carry both tactile and optical sensors, are of increasing importance in coordinate measurement technology. A combination of tactile and optical sensors makes it possible to combine the advantages of the high accuracy of a tactile measurement system with the speed of an optical measurement system in a single coordinate measuring device. Furthermore, calibration processes when changing sensors are avoided, as is possible reclamping of a workpiece.
Conventionally, the sensor head, which may also be referred to as a sensor system, is connected to a carrier system which supports and moves the sensor system. Various carrier systems are known in the prior art, for example portal systems, stand, horizontal arm and arm systems, all types of robotic systems and finally closed CT systems in the case of sensor systems operating with X-rays. The carrier systems may comprise further system components which permit maximally flexible positioning of the sensor head. One example of this is the rotation/swivel articulation of the Applicant marketed under the reference “RDS”. Furthermore, various adapters may be provided in order to connect the different system components of the carrier system to one another and to the sensor system.
In the context of the present invention, a “system component” is intended to mean any such element of the carrier system and the sensor head per se. Thus, the sensor head as such forms a system component. Furthermore, for example, an adapter as such forms a system component, a rotation/swivel articulation forms a system component, a portal of a portal structure forms a system component, a changer magazine forms a system component, etc. The present invention therefore relates to all interface arrangements of any two such system components.
In coordinate measuring devices having tactile sensor systems, in order to couple two system components a so-called “adapter plate” or adapter surface is conventionally provided on each of the system components. The adapter surfaces are configured in such a way that they can be applied on one another and permit interchange of data in two directions, for example measurement data and/or control signals. Conventionally, these adapter surfaces are constructed according to a particular pattern or standard, in order to be able to couple different system components arbitrarily to one another, for example different sensor heads on a rotation/swivel articulation, etc. Besides this, it is also important for the adapter surfaces to be arranged relative to one another as accurately reproducibly as possible. Otherwise, the calibration outlay after replacing a system component would increase enormously. In general, a so-called three-point bearing is used for this, which advantageously provides three bearings respectively offset by 120° from one another, distributed over the adapter surface. Each of these bearings limits a lateral movement of the adapter surfaces of the two system components to be coupled to one another, so that a unique orientation and arrangement of the two system components relative to one another is made possible. The three-point bearing is generally provided with an outer, in particular annular, outer region of the adapter surfaces. The outer region encloses a central region. An electromagnetic holding device is generally provided in this central region. In this case, one system component, in particular the system component on the carrier system side, comprises an electromagnet and the other system component, generally the system component on the sensor head side, comprises an armature disk or flux guiding parts. In this way, the two system components can be pressed onto one another firmly in the three-point bearing by means of the electromagnet. Of course, coupling by means of two permanent magnets is also possible.
So far, the data rate for transmission has been limited to about 80 to 100 megabits. This, however, is too low for data transmission of modern camera systems, since an image size of one megapixel and a resolution of 8 bits per image incurs 1 MB of data. A data rate of 25 or 50 images therefore respectively entails 50 megabits or 400 megabits of data for transmission. This is more than can at present be transmitted with modern radio transmission paths. Standard technologies currently end there at 300 megabytes for second generation WLAN. Furthermore, radio transmissions usually cannot be carried out continuously with full bandwidth, which makes continuous measurement even more difficult, or even prevents it. With known technologies, consequently, efficient transmission of large image data quantities is scarcely possible. In this context, relatively large sensors comprising several megapixels as well as data rates at 100 to 150 Hz are usual in modern camera systems. Likewise, there is a trend toward higher digital resolutions of 10 bits or 12 bits, which correspondingly increases the amount of data involved, even in the case of relatively small sensors.
In machine tools, radio transmission systems are often used for coordinate measurement data. However, since only tactile sensors are used in this case, the data rates are much lower. Typically, only a few hundreds of measurement points are then taken per second. This data transmission is therefore readily possible with standardized conventional radio transmission systems. The problem for the coordinate measuring devices thus arises specifically when the sensor used is suitable for fast measurements and therefore also high data rates. This problem hence occurs particularly in the case of fast-scanning or optical sensors. Fast-scanning sensors usually operate optically and involve individual detectors or detector arrays, as can be produced for example with cameras based on CCD or CMOS. Here, therefore, the same task always typically arises of transmitting large incurred amounts of data rapidly, efficiently and with the least possible interference by the system to the evaluation unit.
Furthermore, documents DE 10 2004 014 153 A1, EP 0 362 625 A2, DE 200 08 721 U1 and WO 2008/098716 A1 disclose devices for coupling various objective arrangements onto an optical sensor head.
To date, however, the prior art has lacked interface arrangements which permit flexible arrangement of both tactilely and optically measuring sensor heads in coordinate measuring devices with effective energy transmission and high data transmission rates.